Project description:Hepatic fibrosis is a wound-healing response to chronic liver injury, which may result in cirrhosis and liver failure. The c-Jun N-terminal kinase-1 (JNK1) gene has been shown to be involved in liver fibrosis. Here, we aimed to investigate the molecular mechanism and identify the cell-type involved in mediating the JNK1-dependent effect on liver fibrogenesis Wild-type (WT), JNK1−/− and JNK1Δhepa (hepatocyte-specific deletion of JNK1) mice were subjected to bile duct ligation (BDL). Additionally, we performed bone marrow transplantations (BMT), isolated primary hepatic stellate cells (HSCs) and studied their activation in vitro. Serum markers of liver damage (liver transaminases, alkaline phosphatase and bilirubin) and liver histology revealed reduced injury in JNK1−/− compared to WT and JNK1Δhepa mice. Hepatocyte cell death and proliferation was reduced in JNK1−/− compared to WT and JNK1Δhepa. Parameters of liver fibrosis such as Sirius Red staining as well as Collagen IA1 and αSMA expression were down-regulated in JNK1−/− compared to WT and JNK1Δhepa livers, 4 weeks after BDL. To delineate the essential cell-type, we performed BMT of WT and JNK1-/- into JNK1-/- and WT mice, respectively. BMT experiments excluded bone marrow derived cells from having a major impact on the JNK1-dependent effect on fibrogenesis. Hence, we investigated primary HSCs from JNK1−/− livers showing reduced transdifferentiation compared with WT and JNK1Δhepa-derived HSCs. We conclude that JNK1 in HSCs plays a crucial role in hepatic fibrogenesis and thus represents a promising target for cell-directed treatment options for liver fibrosis. Control (JNK1f/f), JNK1 null (JNK1-/-) and hepatocyte-specific JNK1 null (JNK1Δhepa) mice were subjected to control, acute and chronic injury, i.e. sham or bile-duct ligation for 48h or 28 days resp., whereafter gene expression profiles were determined.
Project description:Hepatic fibrosis is a wound-healing response to chronic liver injury, which may result in cirrhosis and liver failure. The c-Jun N-terminal kinase-1 (JNK1) gene has been shown to be involved in liver fibrosis. Here, we aimed to investigate the molecular mechanism and identify the cell-type involved in mediating the JNK1-dependent effect on liver fibrogenesis Wild-type (WT), JNK1−/− and JNK1Δhepa (hepatocyte-specific deletion of JNK1) mice were subjected to bile duct ligation (BDL). Additionally, we performed bone marrow transplantations (BMT), isolated primary hepatic stellate cells (HSCs) and studied their activation in vitro. Serum markers of liver damage (liver transaminases, alkaline phosphatase and bilirubin) and liver histology revealed reduced injury in JNK1−/− compared to WT and JNK1Δhepa mice. Hepatocyte cell death and proliferation was reduced in JNK1−/− compared to WT and JNK1Δhepa. Parameters of liver fibrosis such as Sirius Red staining as well as Collagen IA1 and αSMA expression were down-regulated in JNK1−/− compared to WT and JNK1Δhepa livers, 4 weeks after BDL. To delineate the essential cell-type, we performed BMT of WT and JNK1-/- into JNK1-/- and WT mice, respectively. BMT experiments excluded bone marrow derived cells from having a major impact on the JNK1-dependent effect on fibrogenesis. Hence, we investigated primary HSCs from JNK1−/− livers showing reduced transdifferentiation compared with WT and JNK1Δhepa-derived HSCs. We conclude that JNK1 in HSCs plays a crucial role in hepatic fibrogenesis and thus represents a promising target for cell-directed treatment options for liver fibrosis.
Project description:Background & Aims: Rapid induction of beta-PDGF receptor (beta-PDGFR) is a core feature of hepatic stellate cell activation, the hallmark of liver fibrogenesis. However, biological consequences of the induction are not well characterized. We aimed to determine the involvement of beta-PDGFR-mediated molecular pathway activation on hepatic stellate cells in liver injury, fibrogenesis, and carcinogenesis in vivo. Methods: Loss and constitutive activation of beta-PDGFR were assessed in mouse models with either a stellate cell-specific beta-PDGFR knockout or the expression of an autoactivating mutation respectively. Liver injury and fibrosis were induced in two mechanistically distinct models: carbontetrachloride (CCl4) treatment and ligation of the common bile duct. Hepatocarcinogenesis with underlying liver injury/fibrosis was assessed by a single dose of diethylnitrosamine (DEN) followed by repeated injections of CCl4. Genome-wide expression profiling was performed isolated stellate cells from these models to determine deregulated pathways. Results: Depletion of beta-PDGFR in hepatic stellate cells led to decreased histological liver injury, serum transaminases, collagen alpha 1(I) and alpha smooth muscle actin expression, and collagen deposition. Stellate cell proliferation was significantly reduced after acute hepatic injury in vivo. In contrast, autoactivation of beta-PDGFR in stellate cells accelerated liver fibrosis, most prominently after 6 weeks of CCl4 induced injury. There was no difference in development of DEN-induced pre-neoplastic loci according to the status of beta-PDGFR. Conclusions: Depletion of beta-PDGFR in hepatic stellate cells attenuated the development of liver injury, fibrosis, and stellate cell proliferation in multiple animal models, whereas the constitutive activation of beta-PDGFR enhanced fibrosis. However, manipulation of beta-PDGFR alone did not reduce development of dysplastic nodules. These findings indicate that titration of receptor beta-PDGFR expression on stellate cells parallels fibrosis and injury, but may not impact the development of hepatic neoplasia alone. Hepatic stellate cells were isolated from liver of beta-PDGFR-wild-type or knockout mice, and treated with beta-PDGF ligand or vehicle control.
Project description:The molecular determinants of a healthy human liver cell phenotype remain largely uncharacterized. In addition, the gene expression changes associated with activation of primary human hepatic stellate cells, a key event during fibrogenesis, remain poorly characterized. Here, we provide the transriptomic profile underpinning the healthy phenotype of human hepatocytes, liver sinusoidal endothelial cells (LSECs) and quiescent hepatic stellate cells (qHSCs) as well as activated HSCs (aHSCs) We assess the transcriptome for purified, non-cultured human hepatocytes, liver sinusoidal cells (LSECs) and quiescent hepatic stellate cells (qHSCs) as well as culture-activated HSCs (aHSCs). Hepatocytes (n=2 donors), LSECs (n=3), qHSCs (n=3) and in vitro activated HSCs (n=3; from the same donors as the qHSCs and LSECs) were used for this study.
Project description:The molecular determinants of a healthy human liver cell phenotype remain largely uncharacterized. In addition, the gene expression changes associated with activation of primary human hepatic stellate cells, a key event during fibrogenesis, remain poorly characterized. Here, we provide the transriptomic profile underpinning the healthy phenotype of human hepatocytes, liver sinusoidal endothelial cells (LSECs) and quiescent hepatic stellate cells (qHSCs) as well as activated HSCs (aHSCs) We assess the transcriptome for purified, non-cultured human hepatocytes, liver sinusoidal cells (LSECs) and quiescent hepatic stellate cells (qHSCs) as well as culture-activated HSCs (aHSCs).
Project description:Sex differences in liver gene expression are dictated by sex-differences in circulating growth hormone (GH) profiles. Presently, the pituitary hormone dependence of mouse liver gene expression was investigated on a global scale to discover sex-specific early GH response genes that might contribute to sex-specific regulation of downstream GH targets and to ascertain whether intrinsic sex-differences characterize hepatic responses to plasma GH stimulation. RNA expression analysis using 41,000-feature microarrays revealed two distinct classes of sex-specific mouse liver genes: genes subject to positive regulation (class-I) and genes subject to negative regulation by pituitary hormones (class-II). Genes activated or repressed in hypophysectomized (Hypox) mouse liver within 30-90min of GH pulse treatment at a physiological dose were identified as direct targets of GH action (early response genes). Intrinsic sex-differences in the GH responsiveness of a subset of these early response genes were observed. Notably, 45 male-specific genes, including five encoding transcriptional regulators that may mediate downstream sex-specific transcriptional responses, were rapidly induced by GH (within 30min) in Hypox male but not Hypox female mouse liver. The early GH response genes were enriched in 29 male-specific targets of the transcription factor Mef2, whose activation in hepatic stellate cells is associated with liver fibrosis leading to hepatocellular carcinoma, a male-predominant disease. Thus, the rapid activation by GH pulses of certain sex-specific genes is modulated by intrinsic sex-specific factors, which may be associated with prior hormone exposure (epigenetic mechanisms) or genetic factors that are pituitary-independent, and could contribute to sex-differences in predisposition to liver cancer or other hepatic pathophysiologies.
Project description:Background & Aims: Rapid induction of beta-PDGF receptor (beta-PDGFR) is a core feature of hepatic stellate cell activation, the hallmark of liver fibrogenesis. However, biological consequences of the induction are not well characterized. We aimed to determine the involvement of beta-PDGFR-mediated molecular pathway activation on hepatic stellate cells in liver injury, fibrogenesis, and carcinogenesis in vivo. Methods: Loss and constitutive activation of beta-PDGFR were assessed in mouse models with either a stellate cell-specific beta-PDGFR knockout or the expression of an autoactivating mutation respectively. Liver injury and fibrosis were induced in two mechanistically distinct models: carbontetrachloride (CCl4) treatment and ligation of the common bile duct. Hepatocarcinogenesis with underlying liver injury/fibrosis was assessed by a single dose of diethylnitrosamine (DEN) followed by repeated injections of CCl4. Genome-wide expression profiling was performed isolated stellate cells from these models to determine deregulated pathways. Results: Depletion of beta-PDGFR in hepatic stellate cells led to decreased histological liver injury, serum transaminases, collagen alpha 1(I) and alpha smooth muscle actin expression, and collagen deposition. Stellate cell proliferation was significantly reduced after acute hepatic injury in vivo. In contrast, autoactivation of beta-PDGFR in stellate cells accelerated liver fibrosis, most prominently after 6 weeks of CCl4 induced injury. There was no difference in development of DEN-induced pre-neoplastic loci according to the status of beta-PDGFR. Conclusions: Depletion of beta-PDGFR in hepatic stellate cells attenuated the development of liver injury, fibrosis, and stellate cell proliferation in multiple animal models, whereas the constitutive activation of beta-PDGFR enhanced fibrosis. However, manipulation of beta-PDGFR alone did not reduce development of dysplastic nodules. These findings indicate that titration of receptor beta-PDGFR expression on stellate cells parallels fibrosis and injury, but may not impact the development of hepatic neoplasia alone.
Project description:Liver fibrosis is a reversible wound-healing response to liver injury and hepatic stellate cells (HSCs) are central cellular players that mediate hepatic fibrogenesis. However, the molecular mechanisms that govern this process remain unclear. Here, we reveal a novel cistromic circuit in HSCs comprising the vitamin D receptor (VDR) and SMAD transcription factors that restrains the intensity of hepatic fibrogenesis. Ligand-activated VDR suppresses TGFβ1-induced pro-fibrotic gene expression in HSCs. Administration of a vitamin D analogue, calcipotriol, diminishes the fibrotic response in a mouse model of liver fibrosis, while VDR knockout mice spontaneous develop extensive hepatic fibrosis by age 6 months. Using ChIP-Seq, we find that the anti-fibrotic properties of VDR are due to crosstalk with SMAD, mediated by their co-occupancy of DNA-binding sites on pro-fibrotic genes. Specifically, SMAD binding potentiates local chromatin accessibility to enhance VDR recruitment at the same cis-regulatory elements, which reciprocally antagonizes the interaction between SMAD3 and chromatin and limits the assembly of transcriptional activation complexes at fibrotic genes, a process that is enhanced by the presence of VDR agonists. These results not only establish this coordinated VDR/SMAD cistromic circuit as a master regulator of hepatic fibrogenesis, but also support VDR as a potential drug target to ameliorate liver fibrosis. Identification of VDR, SMAD3 and H3 binding sites in human stellate LX2 cells that were pre-treated with calcipotriol (100nM) for 16 hrs (where calcipotriol treatment is indicated) followed by incubation of calcipotriol (100nM) or TGFβ1 (1ng/ml) for another 4 hours (where indicated).
Project description:Non-alcoholic steatohepatitis (NASH) is associated with hepatic steatosis, intralobular inflammation, and fibrosis. The degree of hepatic fibrosis, mainly caused by excessive production of extracellular matrix proteins, is the sole predictor of liver-related and overall mortality in NASH patients. The hepatic stellate cells (HSCs) are causally implicated in fibrogenesis during NASH development but as sinusoidal pericytes also vital for vascular homeostasis of the healthy liver. Using single-cell RNA-sequencing we have analyzed whole liver plasticity and interrogated the transition of HSCs from pericytes in the healthy liver to collagen-producing cells in a diet-induced murine model of advanced NASH. We show how postprandial cues are sensed and integrated by HSCs promoting their phenotypic stabilization and, through paracrine mediators, sinusoidal health. While dominant under healthy conditions the basis for this multimodal signaling through stellate cell-specific Gs protein-coupled receptors and the bile-acid receptor NR1H4/FXR deteriorates in activated HSCs of the NASH liver. Expression of key signaling components were validated in situ in human and murine liver tissue supporting the translatability of our findings and pharmacological relevance in treatment of chronic liver diseases as NASH.